In a reformer designed from the start to operate with an open flame reaction zone above a catalyst bed, the gas velocity through the reformer is high enough to move catalysts, leading to erosion of the catalysts and erosion of the refractory of the reformer. When a reformer is converted from having a catalyst bed but no open flame reaction zone above the catalyst bed, to having the catalyst bed and an open flame reaction zone above the catalyst bed, this situation is exacerbated by the even higher gas velocities in the converted reformer. In such a converted reformer, the gas velocities may even be high enough to move the original bricks or tiles in the brick or tile layer which is typically used to inhibit movement of the catalyst particles in the catalyst bed. This causes erosion of the refractory. In addition, pieces of the refractory above the tile or brick layer and sometimes pieces of the tiles or bricks break loose and can then be whirled around the inner periphery of the reformer, in an annular zone extending from the tile or brick layer upwards for a short distance, e.g. about 30 cm.
The present invention proposes solutions to the abovementioned problems, which include trapping the whirling solid objects and changing the physical characteristics of the brick or tile layer. U.S. Pat. No. 3,645,700 provides an improved vessel for fluidised bed reactions, characterised by the provision of metal or non-metal projections of various shapes at calculated intervals on the internal side wall of the vessel. U.S. 3,645,700 thus teaches the prevention of wear of the internal surface of the wall by contacting the projections with the fluidised solid particles, whereafter the solid particles are deflected from the projections without directly contacting the reactor wall. This document is thus not concerned with solid objects whirling around in an annular zone or with reducing the movement of the tile or brick layer and the underlying catalyst of a fixed bed reactor. U.S. Pat. No. 5,016,576 discloses a combustion chamber for combusting fine-grained fuels in a fluidised bed. The combustion chamber has a refractory lining provided at its top end with a cornice, which is enlarged in width. The method employed by U.S. Pat. No. 5,016,676 is to build up a protective body or bed of the fuel solids on the cornice covering the most highly endangered region of the combustion chamber wall and the use of a cornice as described in U.S. Pat. No. 5,016,576 will not solve the abovementioned problems. DE 3117195 discloses a process and apparatus in which the heat, material and momentum exchange in the direct vicinity of the wall of a fluidised bed reactor is reduced. This is achieved by increasing the flow resistance for the fluid in the vicinity of the wall to such an extent that in this area the fluidised bed is no longer boiling. DE 3117195 thus does not deal with solid objects whirling around in an annular path nor with the unwanted movement of catalysts in a fixed bed nor the movement of the tile or brick layer above the catalyst bed. JP 08110007 relates to a heat exchanger which includes tube walls and loop pipes and discloses the use of an erosion baffle to prevent excessive abrasion of the bent ends of the loop pipes by coal ash. JP 08110007 does not propose a solution for dealing with solid objects whirled around in an annular zone against the interior surface of a process vessel. U.S. Pat. No. 4,954,402 discloses a retarder for preventing the erosion of refractory material at a refractory corner over which fluid flows. The retarder is embedded within the refractory material and U.S. Pat. No. 4,954,402 thus does not propose any solutions to the abovementioned problems.